This invention relates to a cordless powered ratchet wrench. In particular, it is an improved battery-powered device for driving a shaft that can accept bits for wrenches, screwdrivers and the like, and that permits ratcheting action to assist an operator in tightening or loosening a threaded object manually to start or finish a job, the preponderance of which is performed under power from the battery. Exposed terminals on the powered cordless ratchet wrench make contact with matching terminals in a charger to permit the battery to be charged upon insertion of the powered cordless ratchet wrench into a charger.
The availability of economical battery cells that can be recharged repeatedly has led recently to the development of a number of battery-powered portable power tools. Such tools eliminate the hazards of electric shock to an operator in contrast to electric tools that are connected to the ac power line. They also add a dimension of convenience in that the user is not restricted to an extension cord or the location of an ac power outlet. The requirements for such a tool include a housing that is adequate to contain a rechargeable battery, means for recharging the battery, and means for reducing the relatively high rotational speed of the motor to a speed that is appropriate for operating the particular rotating tool that is selected. For most applications involving portable electric drills, which are typically constructed with a pistol grip and a trigger switch, all of the torque is normally applied from the motor, and the operator only applies a resisting torque to hold the drill in position. If the drill is to be used only for drilling holes, it is not necessary to reverse the direction of rotation, although this is a useful convenience in cordless electric drills that are also adapted to serve as power screwdrivers, and reversal can help to extract a drill bit from a drilled hole.
A cordless powered wrench, in contrast, has different requirements. It is designed primarily for inserting and removing nuts, bolts, cap screws and the like. A cordless powered wrench, therefore, must be capable of some form of reversal of operation to allow nuts and bolts to be screwed or unscrewed and to allow for the possibility of operation of nuts or bolts having left-handed threads. In addition, typical operation of a wrench of any kind calls for a higher value of torque upon starting to unscrew a nut or bolt or upon finally tightening a nut or bolt. This is effectively accomplished by combining the cordless wrench with a ratchet feature that permits an operator to use the cordless wrench as a manually powered ratchet wrench to start or seat nuts and bolts. An example of such a ratchet is shown in U.S. Pat. No. 2,701,977, entitled "Reversible Ratchet Wrench," which is incorporated here by reference as if set forth fully. The '977 patent teaches a plunger containing steps that serve as teeth to drive the wrench in one direction and as ratcheting teeth that permit the wrench to turn freely in the other direction. The directions are reversed by sliding the plunger.
A powered wrench is difficult and expensive to construct if it is driven through a ratchet. However, at least a limited amount of ratcheting action makes a power tool much more useful than one that lacks ratcheting. A ratcheting feature allows the operator to turn a nut or bolt through a substantial range of rotation by operating the tool repeatedly back and forth through a more limited range of rotation. However, the use of a full ratchet in a cordless wrench represents a source of manufacturing complications, unreliability of the tool, and often excessive noise of operation.